Assessment Comments
Assessment is based on results of ambient water quality and fish tissue monitoring from 2002-04 and fish kill reporting conducted by Iowa State University as part of the ACOE's Des Moines R./Saylorville Reservoir/Red Rock Reservoir water quality study.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "fully supporting" based on results of routine monitoring for indicator bacteria (E. coli). The Class B(WW) aquatic life uses remain assessed (monitored) as "not supported," due to repeated fish kills downriver from Red Rock Dam. The fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2002, 2003, and 2004. The assessments of support of the beneficial uses are based on results of water quality monitoring, fish contaminant monitoring, and fish kill reporting conducted downstream from Red Rock Reservoir during the 2002-2004 assessment period by Iowa State University (under contract with the U.S. Army Corps of Engineers) at ISU/ACOE Station 9 at the Howell Station Landing (STORET station 17630001). This monitoring was conducted as part of the Des Moines River Water Quality Study (see Lutz and Cummings 2003, Lutz 2004, and Lutz et al. 2005).
EXPLANATION: Class A uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from the ISU/ACOE station 0.7 mi downstream from Red Rock Dam. Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of the 2006 Section 305(b) assessments and Section 303(d) listings.
At this monitoring station, the geometric mean of the 26 samples collected during summers of 2002, 2003 and 2004 was 9 orgs/100 ml, with only one sample exceeding the 235 organism/100 ml single sample maximum. These results, combined with results of previous monitoring, continue to indicate extremely low levels of indicator bacteria in this reach of river. According to U.S. EPA guidelines for Section 305(b) reporting, if the geometric mean of E. coli is less than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
Results from this ISU/ACOE monitoring station also suggest that the Class B(WW) aquatic life uses are "fully supported "; however, the Class B(WW) aquatic life uses remained assessed as "not supported" due to repeated fish kills in this river segment. No violations of Class B(WW) water quality criteria for conventional parameters (dissolved oxygen, pH, ammonia-nitrogen) occurred in the 66 samples collected at this station during the 2002-2004 assessment period. Also, none of the 12 samples analyzed for toxic metals violated Class B(WW) criteria.
No fish kills were reported for the 2002-2004 assessment period. Two fish kills, however, were reported for this river reach during the 2000-2002 assessment period. These kills occurred on May 24, 2000 and August 14, 2001 immediately downriver from Red Rock Dam. Both kills were relatively minor and involved channel catfish, freshwater drum and/or white bass. Fish killed in both events exhibited signs of gas bubble trauma (see Lutz et al. 2001:175 and Lutz and Esser 2002:207). According to IDNR's assessment/listing methodology, if no fish kill has occurred over the last three years (2002-2004), good cause for impaired waters de-listing exists, and the assessment should be considered “evaluated” (i.e., of lower confidence) and moved out of impairment categories in the Integrated Report (I.e., categories 4 and 5). Due, however, to the history of fish kills in the tailwater of Red Rock Dam related to gas bubble trauma, the Class B(WW) uses of this segment will remain assessed as "impaired" and will remain in an impairment category of Iowa's Integrated Report (4c).
Fish contaminant monitoring conducted downstream from Red Rock Reservoir by ISU/ACOE in 2002, 2003, and 2004 showed low levels of contaminants (dieldrin, heptachlor epoxide, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish and fillets of common carp. In addition to these pesticide parameters, composite samples fillets from common carp and channel catfish from this station were analyzed in 2004 for mercury (the first analysis of fish tissue samples for mercury conducted as part of the ISU/ACOE program since 1994). Based on this information, fish consumption uses are assessed as "fully supported". The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 2002, 2003, or 2004 ISU/ACOE sampling (or from previous ISU/ACOE monitoring) conducted in the segment of the Des Moines River immediately downstream from Red Rock Reservoir: the levels of contaminants (chlordane and mercury) do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
For more information on ISU/ACOE water quality monitoring in this river reach, see (see Lutz and Cummings 2003, Lutz 2004, and Lutz et al. 2005).
